Fruit Morphometric and RAPD Evaluation of Intraspecific Variability in Some Accessions of African Yam Bean (Sphenostylis stenocarpa Hochst. ex. A. Rich. Harms)

Abstract

African Yam Bean (AYB) (Sphenostylis stenocarpa, Hochst. ex A. Rich, Harms) is an indigenous underutilized legume mainly grown in Sub-saharan African as a source of protein. Intraspecific variability studies were carried out on 10 accessions of AYB obtained from the International Institute of Tropical Agriculture (IITA) Ibadan, Nigeria. Fourteen (14) fruit morphometric characters and nine (9) arbitrary RAPD primers were employed for evaluation of genetic intra-specific variability among the accessions. A total of 410 bands were generated with 261 (63.66%) polymorphic bands. There is significant correlation among some reproductive characters; days to 50% flowering, pods per peduncle, number of locules per pod, number of seeds per pod, pod length and seed set percentage. These characters represent good markers of the taxon suitable for breeding and genetic improvement purposes. Morphometric and RAPD cluster analysis using UPGMA resulted in a dendrogram each; with membership similarity ranging from 72% to 93%. Two accessions (TSs56 and TSs94) recorded higher level of similarity index of 93% based on RAPD profiling. The morpho-metric evidences shows inherent stability of AYB across varied eco-geographical settings, which demands further investigation and exploitation. However, the RAPD evidences show that the species have evolved and adapted to distinct geographical setting with a clear Nigeria and Ghana demarcation. This fact can be engaged to guide future studies, germplasm collection, characterization, documentation, utilization and conservation of AYB to boost knowledge and awareness on the genetic diversity and utility of the species.